Process for separating cobalt and nickel from ammoniacal solutions



United dates PROCESS FOR SEPARATING COBALT AND NICKEL FROM AMMONIACAL SOLUTIONS No Drawing. Application May'Zl, 1958 Serial No. 736,936

1 Claim. c1. =75+-108) This invention relates to the separation of nickel and cobalt from an ammoniacal solution in which they. are dissolved and more particularly to a process in which the cobalt is selectively precipitated from the solution to provide eventually a nickel compound containing so little cobalt as to be commercially acceptable to a greater extent than heretofore.

A prior alt process is known wherein nickel is extracted from nickeliferous ores containing some cobalt by reducing such ores in a furnace, next leaching the calcined ores in an ammoniacal. solution to extract the nickel and the cobalt, and finally distilling the decanted product liquor to cause'the'nickel and cobalt to precipitate as nickel and cobalt compounds. 'In theory, such compounds will precipitate sequentially from the product liquor during distillation if most of the'cobalt is in either the cobaltousor cobaltic state-=and can be thereafter selectively filtei'edfromthe"liquor. In actual practice,

however, the two precipitates form practically: simultaneously= because of the presence in the-product liquorof certain sulfur contaminants which tend. so toafiect the cobalt as to distribute' it between the two -states. It is therefore not commercially practical to -'separate=-'thenickel and the cobalt by the known process so that after the intermixed nickel and cobalt-compounds are calcined to formoxides of nickel and-cobalt, the combined'oxides,

which are mainlynickel, areemployed in industrywhereever the amount of contained cobalt is deleterious. 1

The foregoinginability to' separate the cobalt=from the nickel acreates anumberof disadvantages. :Thus, if the amountof cobalt-in the ore is so great that-the finished commercially acceptableprodu'ct. .However, this remedy has the effect-of simultaneously lowering the amount of nickel eventually. recovered leading to wastage of the" nickel which ends up in the plant tailings heap.

The present 'invention' contemplates the use of an additivesto theiammoniacal product liquorwhich will definitely precipitate practically all of the cobalt from the liquor:beforefithe nickel, wherebyc'the'latter is recoverable in theftformrof a relatively pure: compound.

not considered Additives which successfully meet this objective and which'ipermiti selective:precipitation of thecobalt' from the product liquor with very little coprecipitation Iof nickel'are:fouiidcamongthet insoluble solid. sulfides such as nickel sulfide (;NiS.) \and ferroussulfide (FeS). f "Other insolubleii-solid precipitants which have'beenfound to be successful' 'areelemental; sulfunand sulfidedcalcined nickeli ferous ore;

In copending application Serial No; 736,935, filed May- 21, 1958, it was disclosed that certain gaseous ice and Water soluble sulfides are also effective forthis pufpose.

favors the more selective precipitation of the cobalt and that limited aeration of the product liquor during pre= cipitation by the additive further enhances the selectivity -l of precipitation.

An object of the present inventionis to provide a prooess whereby cobalt is precipitated selectively froman ammoniacal solution containing nickel and cobalt by treating such ,solution'in the presence-of air or oxygen" with an insoluble-sulfideor sulfurbeaiing additive before distillation thereof;

A further object of the-invention is theprovision of a process whereby cobalt is precipitatedselectively from an ammoniacal solution containing nickel and cobalt by treating such solution in the'presence' of air or oxygen with an insoluble sulfide before distillation thereof.

Still another object is to provide a process whereby'co-fbalt is precipitated selectively from an ammoniacal soldtion containing nickelandcobalt by treatingsuch-solw 1 tion with either nickel' sulfide, ferrous sulfide, elemental sulfur, or a sulfided calcined'ore.

Other objects and-:manywof theattendantadvantages of this invention will be readily apprcciated as the same becomes better understood? by reference to the following detailed description. I

The novel process disclosed hereinis intended to be employed in conjunction-withawell-known process for recovering nickel from nickeliferous'ore containing cobalt and iron such as is found in Cuba in considerable quan tities. The ore is dried to reduce substantially the mois ture content, is ground to produce a finely divided mass,

and is fedin'to the itopcfaivertical multiple hearth reduction furnace throughwhich it passes downwardly at a slow -rate.-- Undluted'producer'igas-is introduced at a low point in the furnace andzcombustion gases=maybe introduced at varioushigher levels which causethe ore to be preheated'to a--temperat-ure -of about 600 -C. and then to be slowly heated in areducing' atmosphere to a final temperature between700'. C. and 850 '-C.

The calcined'ore'is cooled after it leaves the furnace and iseventually treated with an ammoniacalsolution to The ammoniacalsolu tion is allowed to settle for a sufficientvtime to permit decantation of a product. liquor containing alarge percentage of the nickel in the ore and much-of the cobalt.- The product liquor is passed through a bubble tower countercurrent to a flow .of steam which distills the leach out the nickel and cobalt.

ammonia and otherdissolved gases from the product liquor thereby causing the nickel and. cobalt to precipitate These carbonates: may then be calcined to form oxides whichare com- As previously pointed out, the nickel generally in the form of carbonates.

mercially useful. and cobalt" co-precipitate and provide a final product which has more limited use than would a nickel product.

having a smaller cobalt content.

The present invention departs from the foregoing process'by treating the product'sliquor after 'decantation and prior to distillationrwith an insoluble solidsulfide such as nickel-sulfide or ferrous 'sulfi'de; or with such an insolublesolid asielemental sulfur-or calcined ore Whichis sulfided'af-ter itleaves the reduction furnace. These addi tives have the effect of causing the cobalt to precipitate 1. immediately, and in advance of the nickel, as an insoluble Patented Nov. 17, 1959*? As in the copendingv application, it was found that rapid mixing of the additive with the product liquor J ,in the precipitate.

sulfide which can be separated from the product liquor as by filtration. Very little of the nickelcompounds will precipitate at this time. Thereafter, the clarified liquor can be subjected to distillation to remove ammonia and carbon dioxide which results in precipitation of nickel basic carbonate and sulfates, these precipitates being amenable to further treatment to produce a commercial nickel product relatively free of cobalt. In order to obtain the best results, the additives should be mixed rapidly throughout the product liquor as this will cause precipitation to take place simultaneously throughout the liquor. Furthermore, countercurrent flow of the sulfide additive with respect to the product liquor reduces the quantity of sulfides required. Treating the product liqnor to reduce most of the cobalt to the cobaltous form before applying the sulfide additive also results in smaller requirements for the additive.

Example I In order to test the efficacy of each of the sulfide additives described above, several product liquors were analyzed to determine their nickel and cobalt contents. Varying amounts of each sulfide precipitant were then added to samples of the product liquors to cause precipitation of the cobalt. The precipitate was then filtered and analyzed to determine the percentage of the original amount of cobalt in the product liquor which was precipitated and also the percentage of the nickel originally in the product liquor which was co-precipitated with the cobalt. The parts of cobalt to one hundred parts of nickel in both the original product liquor and the filtrate were also computed to form a basis of comparison of the profound results produced by the sulfide additives. These results are tabulated in the following table:

Liquor Composition Preelpt- Fll- Precipitate taut trate g. M! g. Col Pts. g. Gorn- Pts. 00/ Percent Percent 100 m1. 100 ml. 100 nts. pound! 100 pts i Co Ni 100 ml. Ni pptd. pptd.

NlS 0.25 2.10 0 0.8 1. 085 .0251 2.31 0.50 0.96 0 51. 4 1. 0 0. 24 0. 4 89. 4 2. 0 0.12 11.2 95. 3

FeS 1.086 .0184 1. B9 0. 96 1. 5 44.1 10 0. 24 11. 3 87. 5

A study of this table indicates that in each instance the sulfide additive causes the selective precipitation of the cobalt in the product liquor with very little co-precipitation of the nickel so that the filtrate in each instance has fewer parts of cobalt to one hundred parts of nickel than did the product liquor which was treated. It can be seen that these additives have the ability to reduce the cobalt in the filtrate to below the desired commercial maximum of one part of cobalt to one hundred parts of nickel without the loss of an infeasible amount of nickel It is also apparent from the results shown in the table that careful control of the amount of sulfide additive employed will produce a filtrate composed essentially of nickel having a commercially acceptable amount of cobalt therein and which is amenable to further treatment to produce compounds useful to industry.

Example 2 Having determined that certain of the insoluble solid sulfides have the ability to selectively precipitate cobalt from an ammoniacal solution containing cobalt and nickel, it becomes desirable to find the cheapest sulfided additive which will perform this function so as to reduce the cost of the final products. It has been found that if the calcined ore as it emerges from the reduction 4 furnace is sulfided, as by passing hydrogen sulfide through the dry calcine or by forming a slurry of the calcine in water and thereafter bubbling hydrogen sulfide through the slurry, the sulfided calcine when mixed with an arnmoniacal solution containing nickel and cobalt will selectively precipitate the cobalt from the solution.

A series of tests were run in which samples of the same product liquor were contacted for two hours with dry untreated calcine, with dry calcine sulfided with hydro gen sulfide, and with calcine in a slurry through which hydrogen sulfide was bubbled. In each case, the amount of nickel and cobalt remaining in the product liquor after treatment was determined as were the percentages of the nickel and cobalt which were precipitated. The parts cobalt to one hundred parts nickel remaining in solution were calculated thereafter for comparison with the product liquor before treatment. The results of these tests are shown in the following table:

Nickel Cobalt Pts. Co] Treatment Pts g./100 ml. Percent g./10O ml. Percent Ni in of solupptd. of solupptd. solution tion tion Product liquor (untreated) 1. 377 .0311 2. 26 100 g. calcine (untreated) 1. 588 0 0230 26. 0 1. 45 Dry calcined-H 8:

100 g. calcine 1. 38-1 0 00594 81. 0 0. 43 50 g 1. 341 2. 6 00586 81. 0 0. 44 25 g 1. 348 2. 1 00763 75. 5 0. 57 Calcine in slurry-I-H S:

100 g. calcine 1. 244 9. 7 00153 95. 2 0.12 50 g 1. 324 3. 9 0126 59. '1 0. 05 25 g 1. 369 0 6 0235 24. 4 1. 72

The foregoing table, in the right column, shows that the calcine when added to the product liquor has the ability to selectively precipitate the cobalt to an extent that the parts of cobalt to one hundred parts of nickel in the product liquor were reduced from 2.26 for the untreated product liquor to a considerably lower figure and in most instances below the desired commercially acceptable figure of one part cobalt to one hundred parts nickel.

It will be noted that even the untreated calcine will selectively precipitate cobalt. This is due to the fact that the calcine even though untreated is lightly sulfided by the hydrogen sulfide contained in both the producer and combustion gases supplied to the reduction furnace. It will be apparent from this that the calcine can be sulfided after It leaves the furnace by passing the producer gases over it thus making it unnecessary to obtain a commercial supply of hydrogen sulfide for this purpose.

It will also be noted that the product liquor leaches some of the nickel from the untreated calcine and from the dry sulfided calcine as will be apparent from the second column of the table wherein the product liquor after treatment with the calcine contains more nickel than it did before treatment. This, of course, is beneficial in that the cobalt to nickel ratio of the treated product liquor is further lowered.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications and alterations may be made therein without departing from the spirit and scope of the invention as set forth in the appended claim.

What is claimed and desired to be protected by Letters Patent of the United States is:

In the recovery of nickel from a cobalt containing nickeliferous ore which has been calcined in a reducing atmosphere, the process of obtaining the nickel content of said calcined ore substantially free of cobalt which comprises sulfiding a portion of said calcined ore, leaching the remainder of said calcined ore in an ammoniacal solution, decanting a product liquor from said ammoni- 2,913,335 I. y Y 5 6 steel solution, mixing with said product liquor in the pres- References Cited in the file of this patent ence of oxygen said sulfided calcined ore to cause a substantial amount of the cobalt in the product liquor to UNITED STATES PATENTS precipitate selectively, and separating the precipitate from 2,722,480 Roy Nov. 1, 1955 the product liquor. 5 2,755,172 McGauley et a1. July 17, 1956 

